The present invention is directed, in general, to systems for monitoring physiological conditions of a person and, more specifically, to systems that are capable of monitoring respiration waveforms, electrocardiogram (ECG) waveforms, blood oxygenation levels, blood glucose levels, movement and position orientation of a body, and other types of physiological information. The present invention is directed toward providing a significant reduction in the power consumption of physiological condition monitors. The present invention is especially useful in providing a significant reduction in the power consumption of battery operated flash memory data storage systems in physiological condition monitors.
Specific types of physiological condition monitors are capable of monitoring specific types of physiological information. For example, one specific type of physiological condition monitor may be capable of monitoring a person""s respiration activity. Other specific types of physiological condition monitors may be capable of monitoring cardiac activity, or blood oxygenation levels, or blood glucose levels, or movement of a body, or position orientation of a body, or other similar physiological conditions. A physiological condition monitor usually comprises one or more appropriate sensors coupled to the body of the person whose physiological conditions are to be measured.
In the case of sensors for detecting respiration activity or cardiac activity, the sensors are capable- of sensing changes in pressure (or changes in other types of physical parameters) that are caused by the person""s breathing and cardiac activity. Physiological condition monitors measure and record waveform signals received from the sensors. Electrocardiogram (ECG) waveform signals are the most commonly used waveforms for measuring a person""s cardiac activity. Respiration waveform signals are used to measure a person""s breathing rate and other types of information concerning respiration.
In the case of sensors for detecting blood oxygenation levels or blood glucose levels, the sensors are capable of sensing changes in the level of oxygen in the blood or changes in the level of glucose in the blood as those changes occur in the person""s blood.
The present invention is capable of providing a significant reduction in the power consumption of any type of physiological condition monitor. For purposes of illustration, however, the present invention will first be described with reference to physiological condition monitors that are capable of monitoring respiration and cardiac activity. It is understood, however, that the present invention is not limited to use in respiration monitors or in cardiac activity monitors.
Low heart rate is referred to as bradycardia. Cessation of respiration is referred to as apnea. When a person exhibits apnea or bradycardia a life threatening condition very likely exists. Physiological condition monitors that are capable of continuously monitoring a person""s respiration and cardiac activity are extremely useful for quickly detecting apnea or bradycardia. Such physiological condition monitors are also useful for quickly detecting other abnormal conditions such as a high heart rate (known as tachycardia) or a very slow breathing rate or a very high breathing rate.
Infants who are susceptible to sudden infant death syndrome are known to exhibit apnea and bradycardia. Physiological condition monitors that are capable of continually monitoring respiration and cardiac activity are particularly useful in the early detection of apnea or bradycardia in infants. Most physiological condition monitors are equipped with an alarm system to sound an alert when such conditions are detected.
A physiological condition monitor may be coupled directly to a person who is a patient in a hospital bed. In such an arrangement the waveform signals from the sensors coupled to the patient""s body may be sent through wires directly to a detector circuit (and other circuitry) located in a console by the patient""s bed. The wires attached to the patient restrict the patient""s movements.
In other cases it is more practical to provide a physiological condition monitor located in a belt or harness that is to be worn by the person to be monitored. In this type of monitor the waveform signal information from the sensors is transmitted via a radio frequency transmitter to a radio frequency receiver in a base station unit that is located away from the site of the physiological condition monitor. The base station unit contains circuitry for analyzing and recording the waveform signal information. The base station unit contains circuitry for detecting abnormal conditions in the person""s breathing or cardiac activity, such as apnea or bradycardia.
Because of the freedom of movement that this type of monitor provides, it is the preferred type of monitor for monitoring the physiological conditions of infants.
If the data that is acquired by the physiological condition monitor is not transmitted to the base station and recorded there, then the data must be recorded in a memory data storage device located within the physiological condition monitor. To preserve the freedom of movement that is provided by a belt or harness monitor, the memory data storage device within the physiological condition monitor must be battery powered.
One type of battery powered memory data storage device that can be used to record the data is a flash memory data storage system. As will be explained more fully below, the power requirements of prior art flash memory data storage systems have caused them to be inefficient in battery powered applications.
A physiological condition monitor that is capable of recording data in a memory storage device for over an extended period of time is very useful. By recording data over an extended period of time the physiological condition monitor can capture information concerning physiological events that do not occur regularly but occur only sporadically or rarely. A doctor or clinician can use the collected data to identify and evaluate such rare or sporadic physiological events.
For the data recording to have value it must recreate the physiological data in sufficiently fine detail to enable a doctor or clinician to identify and evaluate the physiological events represented by the data. This means that the physiological condition monitor must have a relatively high sampling rate throughout the period of time that the data is being recorded. This means that there will be a large amount of data to store.
There is a direct linear relationship between the amount of data to be stored and the quantity of energy needed to store it. To store a small amount of data requires a correspondingly small amount of electrical power. To store a large amount of data requires a correspondingly large amount of electrical power. In a battery powered memory data storage system in a physiological condition monitor, all of the electrical power must be provided by the battery. In order to collect and record the large amounts of data that are required, it is essential that the electrical power in the battery be conserved and used efficiently.
The present invention is directed toward providing a significant reduction in the power consumption of memory data storage systems used in physiological condition monitors. In particular, the present invention is directed toward providing a significant reduction in the power consumption of battery powered flash memory data storage systems used in physiological condition monitors.
A non-volatile data storage device is one that retains the data stored in it when external power to the device is shut off.
One of the earliest non-volatile storage devices was punched paper tape. One of the most recent technologies for storing data in a non-volatile electronic data storage device is called xe2x80x9cflash memory.xe2x80x9d Flash memory is a programmable semiconductor memory of a type called xe2x80x9cread-mostlyxe2x80x9d memory. Flash memory is so named because of the speed with which it can be reprogrammed. Flash memory uses an electrical erasing technology that can erase an entire flash memory array in a few seconds at most. Data written to flash memory remains in a non-volatile storage mode until the flash memory is deliberately erased. Flash memory requires a relatively high level of current (and a high level of electrical power to provide that current) when data is being written to the flash memory. A typical value of current required by flash memory when data is being written to the flash memory is sixty milliamps (60 mA).
CompactFlash(trademark) memory is a relatively new flash memory data storage system. CompactFlash(trademark) is a registered trademark of SanDisk Corporation. CompactFlash(trademark) memory is very useful in various types of technological applications and represents a significant advance over other flash memory data storage systems for a number of reasons. In comparison with other flash memory data storage systems, CompactFlash(trademark) memory has greater speed, greater durability, and smaller size. It is also packaged in a form that is very compatible with personal computers, especially laptop computers. CompactFlash(trademark) memory makes it possible to store several tens of Megabytes of data on a memory card that is no larger than an ordinary matchbook. CompactFlash(trademark) memory cards are now being used in digital cameras, in personal data assistants (PDAs), in MP3 audio players, and in other similar electronic data storage devices.
One of the drawbacks of CompactFlash(trademark) memory (and of flash memory data storage systems in general) is that its operation requires a relatively high level of current. The greater the speed with which a flash memory data storage system is accessed, the more current it requires for operation. Even at the slowest access speeds, flash memory data storage systems generally require a comparatively large amount of current for operation.
For this reason flash memory data storage systems have not been widely used in battery powered devices for gathering electronic data. This is especially true for battery powered devices that acquire data slowly over a relatively long period of time. The power requirements of a flash memory data storage system in such a device would require continual and frequent replacement of the batteries. In many applications this requirement would make the use of a flash memory data storage system impractical.
It would be advantageous to have a flash memory data storage system in a physiological condition monitor in which the power consumption is reduced compared to the power consumption in prior art flash memory data storage systems. It would also be advantageous that any reduction of the power consumption in such a flash memory data storage system be achieved without a corresponding reduction in the performance level of the flash memory data storage system.
To address the deficiencies of prior art electronic data storage systems in physiological condition monitors, and especially those that require a relatively high level of current (and power) when data is being written to them, it is a primary object of the present invention to provide an improved electronic data storage system in a physiological condition monitor in which the power consumption of the electronic data storage system is reduced compared to the power consumption of prior art electronic data storage systems.
It is also an object of the present invention to provide an improved flash memory data storage system in a physiological condition monitor in which the power consumption of the flash memory data storage system is reduced compared to the power consumption in prior art flash memory data storage systems.
It is a further object of the present invention to provide an improved flash memory data storage system in a physiological condition monitor in which the reduction of the power consumption in the flash memory data storage system is achieved without a corresponding reduction in the performance level of the flash memory data storage system.
It is an additional object of the present invention to provide an improved flash memory data storage system for use in a battery powered device for gathering electronic data in a physiological condition monitor.
It is yet another object of the present invention to provide an improved flash memory data storage system for use in a battery powered device in a physiological condition monitor that acquires data slowly over a relatively long period of time.
Accordingly, in an advantageous embodiment of the present invention, there is provided, for use with a memory data storage device in a physiological condition monitor, where the memory data storage device operates in a high power mode when data is being written therein and operates in a low power mode when inactive, a system for minimizing a power consumption level of the memory data storage device comprising: 1) a controller capable of receiving incoming data to be written to the memory data storage device; and 2) a first low power buffer coupled to the controller, wherein the controller stores the incoming data in the first low power buffer until a predetermined amount of incoming data has been accumulated in the first low power buffer and wherein the controller transfers the accumulated predetermined amount of incoming data to the memory data storage device in a single data transfer.
In one embodiment of the present invention, the predetermined amount of incoming data is determined by a size of the predetermined amount of incoming data.
In another embodiment of the present invention, the size of the predetermined amount of incoming data is five hundred twelve bytes of data.
In still another embodiment of the present invention, the predetermined amount of incoming data is determined by a selected time duration during which the predetermined amount of incoming data has been accumulated.
In yet another embodiment of the present invention, the controller transfers the accumulated predetermined amount of incoming data to the memory data storage device when the memory data storage device is in the high power mode.
In a further embodiment of the present invention, the system further comprises a second low power buffer coupled to the controller capable of storing the incoming data when the accumulated predetermined amount of incoming data is being transferred from the first low power buffer to the memory data storage device.
In a still further embodiment of the present invention, the memory data storage device is of a battery powered type having a relatively high power consumption when data is written to the memory data storage device.
In a yet further embodiment of the present invention, the memory data storage device is a flash memory card.
The foregoing has outlined rather broadly the features and technical advantages of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features and advantages of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art should appreciate that they may readily use the conception and the specific embodiment disclosed as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the invention in its broadest form.
Before undertaking the DETAILED DESCRIPTION OF THE INVENTION, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document: the terms xe2x80x9cincludexe2x80x9d and xe2x80x9ccomprise,xe2x80x9d as well as derivatives thereof, mean inclusion without limitation; the term xe2x80x9cor,xe2x80x9d is inclusive, meaning and/or; the phrases xe2x80x9cassociated withxe2x80x9d and xe2x80x9cassociated therewith,xe2x80x9d as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like; and the term xe2x80x9ccontrollerxe2x80x9d means any device, system or part thereof that controls at least one operation, such a device may be implemented in hardware, firmware or software, or some combination of at least two of the same. It should be noted that the functionality associated with any particular controller may be centralized or distributed, whether locally or remotely. Definitions for certain words and phrases are provided throughout this patent document, those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior, as well as future uses of such defined words and phrases.